1. Field of the Invention
The present invention relates to an optical connector, and more particularly to a multiple-core optical connector which is machine connectable.
2. Background of the Technology
As an optical connector which connects mutually switch-selectable tape-form optical fiber cores, the so-called "optical fiber tape core", such as optical connectors made of plastic (the so-called MT-type optical connector: Mechanically Transferable established, for example, in JIS C 5981 and the like have been provided.
In addition, with a view toward enhancing the connection workability for the optical connector made of plastic (hereinafter, to be referred to as the "plastic connector" ), in the recent years, the so-called MPO connector (optical connector, established in JIS C 8981 and the like, the structure of which encases an optical connector inside of a housing) has been provided.
FIG. 6 and FIG. 7 show an MPO connector 1. In FIG. 7, this MPO connector is of such a structure that it internally supports an optical connector ferrule 2 (hereinafter, to be referred to as the "ferrule") established in JIS C 5981 and the like and a pin clamp 4 clamping a guide pin 3, which has been inserted into the neighborhood of the rear end part (the right side in FIG. 7) of the ferrule 2 of the optical connector ferrule 2, and a pin clamp 4 which clamps a guide pin 3 which penetrates the ferrule 2 in the neighborhood of the rear end part of the ferrule 2 (right side of FIG. 7) and a cylindrical coupling 6 in a cylindrical housing 5, and houses a coil spring 7 for generating butting force inside the coupling 6. The ferrule 2 is movable in the forward and backward directions (left and right directions in FIG. 7) inside the housing 5. The housing 5 is impelled toward the front (middle to left side in FIG. 7) by a spring 8, provided separately for the housing. When the ferrule 2 is pushed towards the inside of the MPO connector 1, if the housing is not driven but is located at the tip position of the MPO connector 1, then the entire body of the ferrule 2 enters the inside of the housing 5. By having an engaging projection 9 projecting from the side surface of the housing 5 detachably engage with the housing on the receiving side, of an optical connector adapter 10 and the like (refer to FIG. 6), the state of being inserted into the housing on the receiving side for the MPO connector 1 can be maintained.
In FIG. 7, reference numeral 11 is a boot and retain a terminated optical fiber 12 (the optical fiber tape core), which is capable of being abutted and connected in the ferrule 2 by the ferrule 2.
In FIG. 7, reference numeral 13 is an optical fiber hole and houses the aforementioned optical fiber 12. This optical fiber hole 13 is in the shape of a square groove, corresponding to the aforementioned optical fiber 12 which is tape-like in its shape.
In the MPO connector shown in FIG. 6 and FIG. 7, since labor is required for the use of dedicated polishing machine in the polishing of the tip of the ferrule 2, assembling the ferrule 2 at the tip of the optical fiber at the site would mean that an extremely large number of man-hours is needed.
Thus, a method whereby the connector polishing work after being connected is omitted, that is, producing the so-called "optical connector for on-site attachment" can be considered by penetrating and anchoring an optical fiber in a ferule with a pre-polished tip. In this form of optical connector, an optical fiber which has been anchored to the ferrule beforehand is pulled out behind (on the side opposite to the tip which has been polished) the ferrule and then is fusion spliced with a separate optical fiber in a subsequent process.
An example of optical connector for on-site attachment which has been already proposed is shown, as follows.
1 An optical fiber connector which is disclosed in Japanese Patent Application No. Hei 6-167274 (U.S. Pat. No. 5,363,461).
For this optical connector, attachment at a work site is made easy, and it consists of a plug and a metal ring in which an optical fiber stub, manufactured beforehand, has been inserted and disposed in an inner hole and the tip of which has been polished, a main body member which houses these components, and an attaching ring. The procedure for on-site assembling consists of insertion of the optical fiber to be connected with the assembly, and once a confirmation as to the fiber is against the optical fiber stub inside the plug, the optical fiber of interest is adhesively fixed with a cement and the like.
Next, by bending the crimp arm and tightly binding the protective covering of the optical fiber arm, the procedure is completed. A refractive index adjusting material is placed in between the optical fibers.
2 An optical connector which is disclosed in U.S. Pat. No. 5,040,867.
This optical connector is provided with a ferrule to which an optical fiber which has been inserted and disposed beforehand at the factory, and alignment parts for the mechanical positioning and connecting the optical fiber inside the ferrule and the external optical fiber. At the assembling site, after passing the optical fiber inside the crimp, assembly is done by inserting the fiber until it is against the optical fiber on the ferrule side.
3 An optical connector which is disclosed in U.S. Pat. No. 4,598,974.
This optical connector has a ferrule into which an optical fiber has been inserted and disposed beforehand at the factory and a connecting chamber having electrodes, which are disposed adjacent to this ferrule and facing each other inside.
In order to connect an optical fiber cable and the optical connector at the site, a bare optical fiber, the optical fiber cable of which the covered tip has been removed, is inserted into the optical connector. When abutment with the optical fibers is completed, discharge between the electrodes is conducted, and the optical fiber on the ferrule side is fusion-spliced to the optical fiber on the optical fiber cable side.
4 An optical connector which can be assembled at the site, which is disclosed in International Patent Application, No. WO 96/31795.
This optical connector is provided with a ferrule, which is built inside the optical fiber, in which a slot has been cut out for fusion of the optical fiber to be inserted. The end of the optical fiber with the built-in ferrule is exposed inside this slot, and when on-site assembling of the optical connector is made, while being observed under a microscope after the tip of the external optical fiber and the tip of the optical fiber with the built in ferule have been abutted, fusion splicing is conducted by a discharge between the electrodes. After the completion of the fusion splicing, connector housing parts are covered at the periphery of the ferrule, thereby completing the optical connector.
As was shown in aforementioned 3 and 4, when the optical fiber with the built-in ferrule and the external optical fiber are fusion spliced, there is the drawback in that because the fusion splicing is a permanent connection, it is not possible to redo a connection. That is, in reconnection work, when the connection loss of the connecting parts and the like exceed the prescribed value and switching the connection with another optical fiber by reusing the ferrule part which was fusion spliced become impossible in actual practice. The tip side of the optical fiber, including the ferrule part, must be cut off and discarded. Consequently, the drawback arises that the optical fiber becomes shorter each time the connection work is repeated.
In addition, although the optical connectors which are disclosed in 1 and 2 are optical connectors of mechanical splicing method, confirmation of the connected parts cannot be made from the outside.
Furthermore, each of these optical fibers are for single-core use, and heretofore there has been no suitable optical connector which is capable of being assembled on site for multiple-core connections, and the development of an optical connector for multiple-core which is capable of being assembled easily on site has been sought.
In the case of housing the fusion-spliced parts, since there is a limit as to the miniaturization of the fusion-spliced parts, there is the problem that it becomes necessary enlarge the parts size for housing a plurality of fusion-spliced parts in the MPO connector, as shown for example in FIG. 6 and FIG. 7.